Apparatus for converting a web into tubular form



R. HERDINA March 17, 1964 APPARATUS FOR CONVERTING A WEB INTO TUBULAR FORM Filed Jan. 28, 1963 Fig. 2

IllttlilllfiiilllliilIlilllilililll'l'lill IN VEN TOR RaBER 7 H'RD/Nfl United States Patent *ice 3,125,008 APPARATUS FOR CONVERTING A WEB INTO TUBULAR FORM Robert Herdina, Vienna, Austria, assignor to Hamac- Hansella Aktiengesellschaft, Viersen, Germany, a corporation of Germany Filed Jan. 28, 1963, Ser. No. 254,168 Claims priority, application Austria Jan. 31, 1962 1 Claim. (Cl. 93-82) This invention relates to a forming element for converting a web of flexible material, such as paper or plastic, into tubular form. Such an element is commonly employed in packaging machinery in which a web of packaging material is formed into a tube, and successive lengths of the tube are filled and sealed to produce individual bag-like packages.

Forming elements of the character described have heretofore consisted of a pipe whose inlet end is provided with an integrally-formed web guide having a curvature and disposition somewhat like that of a coat collar. This web guide provides a rather sharp entrance angle for the web, thus calling for the employment of web material having high tear resistance. The web guide projects laterally from the pipe at a steep downward angle from the entrance rim of the pipe, and as the web material is pulled, during operation of the packaging machine, the guide collar constrains the web to move, first, at a steep upward angle to the rim of the pipe, then at a sharp angle downwardly into the pipe.

Because of their geometrically complex shape, conventional web guides are difficult to manufacture. Moreover, no single shape is suitable for all web materials, because even if the pulling force on the web is constant, different frictional resistances are encountered across the width of the web. This stems from the fact that the angle through which the web is bent as it passes into the pipe differs from point to point, i.e., from the summit of the bending edge to the lowest point, at which the opposite longitudinal edges of the web come into overlapping relation. As a result, the web is not uniformly stressed across its width. The critical point is at the summit of the bending edge where the sharp bending angle creates almost a cutting effect.

Notwithstanding these shortcomings, this type of web guiding equipment, due to its very nature, precludes the employment of gentler bending angles.

When a tube forming apparatus of the character described is used in certain packaging machines the lateral margins of the web are brought into overlapping relationship as a result of formation of the tube, and the overlapping margins are fused to form a longitudinal seam as the tube is moved axially downwards. Its lower end is transversely sealed, it is filled from above with a measured charge of powdered, granular, or chunky material, and a transverse seal is formed at a distance from the lower end, to produce a filled bag or container which is severed from the remainder of the tube. This procedure is then repeated; It is essential that the forming element convert the original web material, without stretching it, into a tube that is smooth and uncreased. More over, the conversion procedure should occur within the shortest possible longitudinal distance so that the material being packaged falls through the shortest possible distance. Apparatus heretofore employed has not met these requirements to a fully desirable degree.

In accordance with this invention, formation of the web into tubular form is brought about by the upper edge of the forming pipe itself. This edge is specially contoured to provide a web-bending edge of predetermined curvature allowing the web to approach the pipe at sub- 3,125,008 Patented Mar. 17, 1964 stantially right angles thereto and which imparts an arched cross-section to the web during its approach. It has been found to be of unusual advantage to employ a bending edge curvature which, in developed form, conforms substantially to a one-half of a sine curve. An apparatus of this kind is not only substantially simpler to design and manufacture, but has the advantage of bending the web more easily and expeditiously. Because of the pre-forming of the web into an arched cross-section as it approaches the bending edge of the pipe, and thereupon bending the. web through substantially a right angle as it is converted into tubular form, the web material is much more flexible and supple in the region of the bending edge.

In one embodiment of the invention the bending edge of the pipe can be provided with a special lip adjacent to and conforming in curvature to the summit region of the edge, adapted to bear the tension exerted upon the web by the pulling action of the machine on the end of the tube. As a result, the web remains untensioned in its lateral regions, and is thus in a relatively limp yet uncreased condition as it is converted from the shape in which it has an arched cross-section to the tubular form. This action is facilitated by making the upper bending edge of the pipe of rounded cross-sectional contour.

In the drawings, in which two embodiments of the invention are shown:

FIG. l is a perspective view of a forming pipe having a bending edge of the character herein-before referred to;

FIG. 2 is a vertical cross-sectional view of the pipe in combination with a web of material in the process of being formed into a tube; and

FIG. 3 is a view similar to FIG. 2 illustrating a modification.

The device illustrated in FIG. 1 comprises a pipe 1 whose upper inlet end lies along an oblique angle to the pipe axis. The upper edge of the pipe defines a bending edge 2 whose curvature, when developed, conforms substantially to the equation 27 21 am. 0 E

tially at right angles to the pipe 1. It passes over the peak or summit 5 of the bending edge 2, and by virtue of the curvature of the latter, the web in the region between the roller 4 and the pipe 1 is deformed into an arch of substantially U-shaped cross-section.

As seen in FIG. 2 the tension applied to the tube in the direction of the arrow 6 is transmitted principally to that part of the web 3 which passes over the summit region 5. The remainder of the web on opposite sides of the region 5 is stressed to a lesser degree and remains more or less limp, especially in the bending edge regions on each side of the region 7 where the marginal edges of the tube overlap. As a result, and especially if a rounded cross-sectional contour is imparted to the bending edge 2, even web materials of low tear resistance can be successfully converted into tubes without difficulty.

For the sake of clarification, lines have been shown extending longitudinally along the curved surfaces of the web and tube.

In accordance with the embodiment of the invention illustrated in FIG. 3, an auxiliary element 8 is arranged immediately adjacent to and on the outside of the summit 5 of the bending edge 2 of the pipe 1. This element is adapted to take up and bear the tension developed in the summit region by the downward pulling action upon the tube, thus relieving the web of tensional stress even in the summit region. This construction is predicated upon the premise that the transmission of the pulling force to the web, in order to advance the same, occurs only along a relatively narrow region passing over the element 8. Between the element 8 and the roller 4 the pulling force is transmitted along diverging lines to the entire width of the web 3. The lateral portions of the web which lie on'each side of the element 8 are more or less devoid of tension and therefore pass around the bending edge 2 with a minimum of friction. The edge 2 is, in this embodiment, also preferably constructed to embody a rounded cross-sectional contour.

The element 8 is advantageously of the same curvature as the summit region of the bending edge 2. It may even have a sharper curvature. In order to bring about the smoothest possible guidance of the web into the pipe as it passes over the summit region, the upper edge of the element 8 can be positioned slightly above the summit 5, as indicated in FIG. 3.

What is claimed is:

A forming apparatus for converting a continuous Web of flexible material such as paper or plastic into tubular form, consisting of a cylindrical pipe having an inlet end oblique to the longitudinal axis of the pipe, means for directing the web toward said inlet endalong a direction substantially perpendicular to said longitudinal axis and then over the summit of said inlet end into and longitudinally through said pipe, the inlet edge being of rounded cross-section and having a contour which when developed conforms substantially to a half of a sine curve, and an auxiliary element closely adjacent to the outer surface of the pipe in the region of the summit of said inlet edge, said auxiliary element conforming in curvature to said summit, and the outer edge of said auxiliary element extending a small distance beyond said inlet edge whereby said auxiliary element causes the tension on said web to be concentrated at its central portion leaving its lateral portions unstressed.

References Cited in the file of this patent UNITED STATES PATENTS 2,899,875 Leasure Aug. 18, 1959 2,940,408 Monsees et a1 June 14, 1960 3,042,103 McDevitt et a1. *July 3, 1962 

